Hemicelluloses are a group of plant-derived heteropolysaccharides, which are associated with cellulose and lignin. The most common hemicelluloses are xylan, glucuronoxylan, arabinoxylan, glucomannan and xyloglucan.
Xylanases catalyze endohydrolysis of the 1,4-β backbone of xylan, a heteropolymer of xylose. Xylanases are naturally produced by organisms such as algae, bacteria, fungi, gastropods and protozoa, which can use xylose as a carbon source for cellular metabolism. See, Prade (1995) Biotech. Genet. Eng. Rev. 13:100-131.
Commercial applications of xylanases in the feed, food/beverage and technical industries (e.g., biomass applications) vary. In the feed industry, xylanases are used in monogastric and ruminant feeds to increase digestibility and nutritive value of poorly degradable feeds (e.g., barley, silage and wheat). In the food/beverage industry, xylanases are used in fruit and vegetable processing to make nectars, purees and juices, in brewing and winemaking to hydrolyze mucilaginous substances in grains for fermentation, and in baking to improve dough quality (e.g., elasticity and strength). In the technical industry, xylanases are used in papermaking to reduce chlorine consumption and toxic discharge during bleaching of wood pulp, in textile processing to reduce or replace chemical retting, and in bioremediation/bioconversion to treat/recycle wastes and to produce biofuels and fine chemicals.
In many of these applications, xylanases are used in connection with various other lignocellulolytic enzymes such as cellulases, hemicellulases, ligninases, pectinases and proteases. Lignocellulolytic enzymes therefore have significant potential applications in the feed, food/beverage and technical industries. New compositions and methods for efficiently processing lignocellulosic materials are needed.